Apparatus for generating power using jet stream wind power

ABSTRACT

A wind energy generator for employment in the jet stream or other wind conditions is described herein. The craft includes an airfoil and at least one wind energy generating device. The craft further includes a variable geometry tail boom unit whose orientation relative to the rest of the craft can be adjusted in accordance with the needs of the user. The craft is tethered to the ground. The wind energy generating devices transferring generated electrical power back to the ground using a conductive transfer line or alternative energy transfer means. The can craft further include an airframe onto which the wind energy generating devices can be mounted the airframe can include an open structured airframe. The invention further describes method of putting an energy generating craft into the air. The method comprises becoming airborne in a vertical configuration, transitioning a tail boom into an orientation parallel to plane of the airfoil and entering a horizontal flight configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/034,425 to Bevirt, filed Mar. 6, 2008.

TECHNICAL FIELD

The invention described herein relates generally to wind powergeneration In particular, the invention relates to devices and methodsfor generating electrical power utilizing the wind energy collected fromthe jet stream. The invention also comprises a method of enabling a windenergy collection craft to use vertical take of and then transition intohorizontal operation during use.

BACKGROUND

The generation of electricity from conventional ground based devices isjust beginning to become commercially viable. However, such ground basedelectrical generation devices are somewhat hampered by the low powerdensity and extreme variability of natural wind currents (in time andspace) at low altitudes. For example, typical average energy density atthe ground is less than about 0.5 watts per square meter (W/m²). Incontrast jet stream energy densities can average about 10 W/m². Also,the large size of ground based rotor blades and slow rotationalvelocities of such ground based rotor systems presents difficultengineering problems not yet solved. Additionally, the presence of suchlarge rotating blades presents something of an ecological hazard toflying birds.

Accordingly, there is a need for wind-driven power generation sourcesthat are both feasible using existing technologies and capable ofgenerating power on an economically sustainable scale. The apparatusesand methods disclosed here present embodiments that solve some of theproblems associated with existing wind powered electricity generationapproaches.

SUMMARY OF THE INVENTION

In accordance with the principles of the present invention, a wind powergeneration device is disclosed.

In one embodiment, the invention comprises a craft tetherable to theground. The craft includes an airfoil and at least one wind energygenerating device including but not limited to wind driven rotorgenerators and turbines. The craft is configured to enable a verticaltake off and enables a rotation of the craft so that it is normal to thewind direction. In another related approach the wind energy generatingdevices are rotated so that the blades are normal to the wind direction.The craft can further include a variable geometry tail boom unit whoseorientation relative to the rest of the craft can be adjusted inaccordance with the needs of the user. The wind energy generatingdevices transfer generated electrical power back to the ground using aconductive transfer line. Embodiments of the craft further include anairframe onto which the wind energy generating devices can be mounted.In some embodiments the airframe comprises an open structured airframeproviding a stable platform for the wind energy generating devices.

In another embodiment a method of putting an energy generating craftinto the air is described. Said method includes becoming airborne in avertical configuration, optionally transitioning a tail boom into anorientation parallel to plane of the airfoil and entering horizontalflight configuration.

These and other aspects of the present invention are described ingreater detail in the detailed description of the drawings set forthhereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description will be more readily understood inconjunction with the accompanying drawings, in which:

FIG. 1 is a simplified perspective view of an embodiment of an openairframe wind power generation craft in accordance with the principlesof the invention.

FIGS. 2( a)-2(d) are a set of side views of an embodiment of a powergeneration craft deploying a variable geometry boom in accordance withthe principles of the invention.

FIG. 3 is another embodiment of a power generating aircraft inaccordance with the principles of the invention.

FIG. 4 is a flow diagram of an embodiment of vertical flight transitionto horizontal flight as employed by the craft of this disclosure.

FIG. 5 is another simplified flow diagram of an embodiment of verticalflight transition to horizontal flight as employed by the craft of thisdisclosure.

It is to be understood that, in the drawings, like reference numeralsdesignate like structural elements. Also, it is understood that thedepictions in the Figures are not necessarily to scale.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention has been particularly shown and described withrespect to certain embodiments and specific features thereof. Theembodiments set forth herein below are to be taken as illustrativerather than limiting. It should be readily apparent to those of ordinaryskill in the art that various changes and modifications in form anddetail may be made without departing from the spirit and scope of theinvention.

The following detailed description describes an embodiment of awind-energy harvesting device for use at many altitudes, but ofparticular utility when used to generate electrical power whenpositioned in the jet stream.

The jet stream includes a family of fast flowing, relatively narrow aircurrents found in the atmosphere around 10 kilometers above the surfaceof the Earth. They form at the boundaries of adjacent air masses withsignificant differences in temperature, such as the polar region and thewarmer air to the south. The jet stream is mainly found in thetropopause, at the transition between the troposphere (where temperaturedecreases with height) and the stratosphere (where temperature increaseswith height). The wind velocity in the jet stream, although variable, isgenerally quite high. These speeds can vary with temperature gradient,altitude and locations and can range from 55 kilometers per hour (kph)to over 400 kph. A common mean range for jet stream velocities is inrange from about 110 kph to 180 kph. In these jet streams lies a vastuntapped potential for wind generated energy. In fact it is estimatedthat wind energy derived from the jet stream can produce 50 times moreenergy than terrestrial wind for a given wind flow cross-section.

One approach is to provide an aircraft that can reach the requiredaltitude and supply the aircraft with wind-powered electrical powergeneration equipment. This energy can then be transmitted elsewhere foruse.

FIG. 1 illustrates one simplified embodiment of such power generationcraft 100. The craft 100 includes a main airfoil 101 and an airframe 102that support a multiplicity of electricity generating wind energydevices 103 (e.g., wind driven rotor generators and wind turbines). Thecraft is tethered to the ground using a tether 105. Also the craft 100includes an adjustable variable geometry tail boom 107 which can be usedto provide stability to the craft at various points during its “flight”.Various details of this craft are discussed as follows.

The craft includes a main air foil 101 which is used to provide lift forthe craft and keep it aloft during its operational lifetime. Airfoils ofmany different sizes, shapes, and geometries can be employed so long asufficient lift and stability can be provided. The airfoil can comeequipped with the full complement of control surfaces if desiredincluding, but not limited to, aileron, flaps, spoilers, flaperons,elevons, and the like. In the depicted embodiment, the airfoil 101features a small cutout 101 c in the airfoil 101 which can accommodatean optional variable geometry boom as it deploys. Although not necessaryto practice the invention, the cutout has certain advantageous uses insome embodiments.

An airframe 102 is attached to the airfoil 101. Although the airframe102 depicted here is an open airframe that passes an airflow through itsinner portions, the inventors contemplate that the airframe 102 can beconstructed in many different configurations. As depicted here, theairframe is constructed in a geometric shape (although this need not beso). In some implementations, various portions of the airframe 102 canbe configured to generate added lift or be configured as ailerons orrudders or other stabilizing features. Also, the inventors contemplatethat appropriate surfaces of the airfoil 101 and airframe 102 could beenhanced with suitably configured lightweight solar panels. As shownhere, the depicted airframe takes an octagonal shape. Moreover, in thisembodiment, electricity generating wind energy devices 103 are attachedto the airframe 102. As depicted here the wind energy devices 103 can bemounted at the vertices of the octagonal airframe 101. It is pointed outthat this is merely an example with many other possibilities beingreadily apparent to those of ordinary skill.

A plurality of wind energy devices 103 are mounted to the airframe 102.The inventors point out that the wind energy devices 103 can instead (orin addition to) be attached to the airfoil 101 if desired. The inventorscontemplate that one common wind energy device 103 would be a winddriven rotor generator having a rotor blade driven to power a generator.Many other approaches can be used with one particularly usefulembodiment being a wind turbine which can generate substantial energy asa wind flow causes the blades 104 of the turbine to rotate. Such windturbines are known to those having ordinary skill in the art and willnot be elaborated upon at this time. It is also pointed out that manydifferent types of wind turbines could be used if desired. Examplesinclude diffuser augmented wind turbines, Magnus rotors, and otherassociated technologies. Moreover, the energy generation capacity ofsuch craft can be augmented by any number of added wind generationdevices or other energy generation device (e.g., light weight solarpanels and the like) known to those having ordinary skill in the art. Insome embodiments of the device, the wind energy devices 103 (forexample, rotor powered alternators or turbines) are configured so thatpower can be provided to the devices enabling the blades to turn andgenerate lift. This lift can be used to move or assist in moving thecraft to the desired position and altitude. For example, a groundsupplied electricity source (or other source, batteries, solar cells,etc.) is used to power the blades 104 to generate sufficient lift tomove (or assist in moving) the craft to its desired location. Anadvantage to using many wind energy devices is that should one or moreof the devices malfunction, the remaining devices offer a reasonablechance of landing the craft without further damage.

Additionally, a tether 105 is attached to the craft to hold it inposition so it does not drift away during energy harvesting. Theinventors contemplate that the tether can be attached to the craft atmany different places. In one particularly attractive (but not limiting)example, the tether is attached at the center of drag for the craft. Ascan be imagined the tether generally needs to be quite long, on theorder of 10-20 kilometers (kms) long. In one example, an 18 km tethercan be employed. The tether 105 needs substantial strength to hold thecraft 100 in place at the desired position. Materials such as Kevlar™have the required strength to weight properties. Also, the inventorscontemplate other materials can be used. In particular, nano-fibermaterials and nano-scale lines may prove to be attractive materials dueto their high strength to weight ratios. Additionally, conductive linesare generally employed to transfer power from the craft 100 down to aterrestrial power collection station. Aluminum, copper, or otherconductive materials can be used. Aluminum is particular, is anattractive candidate due to its low weight. These conductive lines canrun separately down to the collection site or can be affixed with thetether. For example, a coaxial Kevlar and aluminum tether could be usedto accomplish energy transfer and secure the craft in place. Aconductive core or a conductive sheath could be used with the tether.The inventors further contemplate that energy transfer need not betransferred using a conductive line. It is contemplated that a number ofdifferent energy transfer modes could be employed. For example, anenergy beam could also be used to accomplish said energy transfer. Inone such approach, a microwave generator could be installed on the craftand wind generated energy be used to power a microwave generator whichcreates a microwave beam that is projected down to a collection sitewhich is suitably configured to receive the beam and convert it intoelectricity or some other energy.

In some embodiments, the invention includes a configuration suitable forenabling a vertical take off and then enabling a transition to a flightprofile where the rotor blades of the energy generation devices areoriented at the desired angle to the wind direction. For example, in oneembodiment after vertical take off the blades are then oriented normalto the wind direction. This can be accomplished, for example, byallowing the entire craft to rotate until it reaches the desired flightprofile (e.g., normal to wind direction). In another example, therotating blades of the wind energy generation devices can beindependently oriented (independent from the airframe orientation) tothe desired angle relative to the wind direction.

In another embodiment (as depicted in FIG. 1), an adjustable variablegeometry tail boom 107 is employed in operative combination with thecraft 100. The tail boom 107 operates to provide stability to the craft100. The boom can include vertical and horizontal stabilizers. Also,various configurations can include rudders, trim tabs, stabilators,ruddervators, tailerons, and other stabilizing and control elements. InFIG. 1, the adjustable variable geometry tail boom 107 is set in aconfiguration optimized for vertical “flight” and will most commonly bedeployed in this configuration.

However, reference to FIGS. 2( a)-2(d) shows mode of operation enablingthe transition to vertical flight including the use of an optionaladjustable variable geometry tail boom. FIG. 2( a) shows the craft 200on the ground 201 with the tail boom 207 in a folded “up” configuration.As can be seen in this depiction, the wind driven rotor generators(possibly turbines) 103 are oriented with the blades 104 orientedupward. In one embodiment, lift can be applied to the craft 200 bypowering the wind driven rotor generators 103. For example, electricalpower can be supplied through the tether 105. Alternatively, batteriescan be used to power the wind driven rotor generators (if desired thesecan be ejected after use or maintained to store power). Of coursealternative motive sources can be employed. For example, small motors,perhaps powered by fuel cells can be used. The inventors contemplatemany ways of powering the blades 104 to attain the needed lift. Oneadvantage of such configuration is that it enables a substantiallyvertical 205 takeoff profile for the craft. This enables small takeareas and minimizes the likelihood of damage to the craft 200. Invertical flight stability can be provided by varying the power to thevarious blades to enable a substantially level and vertical take off.Additionally, added stability could be provided by counter-rotatingblades.

Referring now to FIG. 2( b) the boom 207 is deployed by extendingdownward. In some embodiments this can occur immediately as the crafttakes off. Alternatively, the boom 207 can be deployed by rotatingdownward 208 once the craft reaches a desired or predetermined altitude.This downward rotation can be effectuated by a small motor and/or withgravitational assistance. Actuation can be provided by many sources. Forexample, the boom can be deployed by using a signal sent from the groundup the tether 105 to the craft 200. In another example, the boom can bedeployed by using a signal sent from the ground via a telecommunicationssource (radio, microwave, laser, etc.) to the craft 200. Also, acondition sensitive set of instructions can initiate the deployment ofthe boom. For example, when the craft 200 reaches a predeterminedaltitude or when it encounters a predetermined wind speed it deploys theboom. FIG. 2( c) depicts the craft 200 when the boom 207 is fullydeployed extending vertically downward.

At this point the craft may be moved into vertical flight. FIG. 2( d)shows the craft 200 having a fully extended boom 207. At this point, thecraft can use the blades or other aerodynamic means to rotate 209 thecraft 200 into a vertical flight configuration. In some embodiments thiscan occur immediately as soon as the boom is fully deployed.Alternatively, the craft 200 can be rotated forward 209 once the craftreaches a desired or predetermined altitude or once a favorable windenvironment has been located. Actuation to rotate forward can beprovided by many sources. For example, a signal sent from the ground upthe tether 105 to the craft 200 may instruct the craft to rotate intovertical flight configuration. As before a signal can be sent from theground via a telecommunications source (radio, microwave, laser, etc.)to the craft 200. Also, an onboard microprocessor can initiate verticalflight using a condition sensitive set of, for example, when the craft200 reaches a predetermined altitude or when it encounters apredetermined wind speed it deploys. Thus, the boom 207 (in fullyextended configuration) is rotated upward so that it extends parallel tothe plane of the airfoil 101 in a horizontal “flight” configuration.

The configuration depicted in FIG. 2( d) depicts an advantageousorientation for generating power with the wind driven rotor generators.Generally, the craft 200 will be oriented to face the oncoming wind 210to maximize power generation. Thus, the boom 207 (in fully extendedconfiguration) is rotated away from the wind while remaining generallyhorizontal and parallel to the plane of the airfoil 101. The applicantspoint out that some embodiments can be configured so that the winddriven rotor generators 103 can be rotated relative to the airframe. Insuch embodiments, the wind driven rotor generators can be individuallytilted upward some number of degrees so that the rotating bladesgenerate lift as well as generate power when the craft 200 isoperational. Also, the entire craft can be angled upwards to can thesame effect of generating both power and lift with the blades.

FIG. 3 depicts another simplified embodiment of a power generation craft300. The craft 300 includes a main airfoil 301 which supports one ormore electricity generating wind energy devices 303 (e.g., windturbines). The craft is tethered to the ground using a tether 305. Aswith the embodiments described above, the craft 300 includes the abilityto transition from a vertical take off mode into a desired flightprofile (for example, oriented normal to wind flow). In anotherembodiment, (depicted here) an adjustable variable geometry tail boom307 can be used to provide added stability to the craft at variouspoints during its “flight”. Various details of this craft are discussedas follows.

As before, the main air foil 301 provides the lift for the craft andkeeps it aloft during its operational lifetime. Airfoils of manydifferent sizes, shapes, and geometries can be employed so long asufficient lift and stability can be provided. The airfoil can comeequipped with the full complement of control surfaces if desired,including but not limited to, aileron, flaps, spoilers, flaperons,elevons, and the like.

Also, the inventors contemplate that appropriate surfaces of the airfoil301 can be enhanced with suitably configured lightweight solar panels.

The wind energy devices 303 are mounted to the airfoil 301. And asbefore wind energy devices 303 can include wind turbines. To these canbe added Magnus type devices including, but not limited to, Magnusrotors. As before, in some embodiments, the wind energy devices 303 (forexample turbines) are configured so that power can be provided to thedevices enabling the blades to turn and generate lift. This lift can beused to move or assist in moving the craft to the desired position andaltitude.

Additionally, a tether 305 as previously described is attached to thecraft to hold it in position so it does not drift away during energyharvesting. Also as before, the inventors further contemplate thatenergy transfer need not be transferred using a conductive line. It iscontemplated that a number of different energy transfer modes could beemployed. For example, an energy beam could also be used to accomplishsaid energy transfer. In one such approach, a microwave generator couldbe installed on the craft and wind generated energy be used to power amicrowave generator which creates a microwave beam that is projecteddown to a collection site which is suitably configured to receive thebeam and convert it into electricity or some other energy.

In the depicted embodiment, an adjustable variable geometry tail boom307 is employed in operative combination with the craft 300. In thisembodiment, the boom 107 is hinged about a rear portion of the airfoil301. The tail boom 307 operates and is configured as before. In FIG. 3,the adjustable variable geometry tail boom 307 is set in a configurationoptimized for vertical “flight” and will most commonly be deployed inthis configuration. Moreover, the boom 307 of the depicted craft 300operates generally as shown in FIGS. 2( a)-2(d).

FIG. 4 in association with FIGS. 2( a)-2(d) generally outlines anoperating methodology for the craft described herein. The craft 200 (asdescribed in FIG. 2( a)) is resting on the ground 201 in readiness totake off. The craft lies in vertical orientation (i.e., propeller blades104 oriented so that the direction of lift is vertically upward) withthe tether 103 secured to the craft. In operation 401 the blades 104 arerotated with sufficient velocity to enable vertical take off of thecraft. The blades are powered by a number of methods described in partabove. Such methods include, but are not limited to supplying electricalpower to wind driven rotor generators to drive the blades. Once thecraft 200 is airborne to a predetermined or desired altitude, the tailboom 207 is deployed (operation 403). The optionally employed tail boom207 can be rotated until it is deployed. Typically, the boom 207 isdeployed when it is generally parallel with the chord line of theairfoil. This exact angle is, of course, set to the angle desired by theoperator of the craft depending on the aerodynamic needs of the craft orof the operator. Once the boom 207 is deployed the craft can be switchedin to horizontal mode. Commonly, this will be done when the craft 200reaches the desired position. However, as can be appreciated by thosehaving ordinary skill, such level “flight” aspect can be selectedwhenever desired. Thus, by rotating the craft to so that the tail israised relative to the airfoil and the craft rotates forward thehorizontal configuration is attained (operation 405). Optional steps caninclude subsequent power generation, descent, and landing.

FIG. 5 provides an even more simplified operating methodology for thecraft described herein. The craft 200 (without the variable geometryboom) rests on the ground in readiness to take off. The craft lies invertical orientation (i.e., propeller blades 104 oriented so that thedirection of lift is vertically upward) with the tether 103 secured tothe craft. In operation 501 the blades 104 are rotated with sufficientvelocity to enable vertical take off of the craft. The blades arepowered by a number of methods described in part above. Such methodsinclude, but are not limited to supplying electrical power to winddriven rotor generators to drive the blades. Once the craft is airborneto a predetermined or desired altitude, the craft is rotated until it isdeployed in the desired flight profile (operation 503). For example, thecraft (or independently the wind energy generators) is rotated so thatthe blades of the wind energy generators are made normal to thedirection of air flow. The exact angle is, of course, variable and setto the angle desired by the operator of the craft depending on theaerodynamic needs of the craft or of the operator. Thus, by rotating thecraft forward the horizontal configuration is attained. Optional stepscan include subsequent power generation, descent, and landing.

The present invention has been particularly shown and described withrespect to certain preferred embodiments and specific features thereof.However, it should be noted that the above-described embodiments areintended to describe the principles of the invention, not limit itsscope. Therefore, as is readily apparent to those of ordinary skill inthe art, various changes and modifications in form and detail may bemade without departing from the spirit and scope of the invention as setforth in the appended claims. Other embodiments and variations to thedepicted embodiments will be apparent to those skilled in the art andmay be made without departing from the spirit and scope of the inventionas defined in the following claims. In particular, it is contemplated bythe inventors that the aircraft described herein may demonstrate a widerange of airframes and are not limited to the specific open airframeoctagonal shape depicted. The inventors also contemplate a variety ofwind powered electricity generators beyond wind turbines. Further,reference in the claims to an element in the singular is not intended tomean “one and only one” unless explicitly stated, but rather, “one ormore”. Furthermore, the embodiments illustratively disclosed herein canbe practiced without any element which is not specifically disclosedherein.

1. An aerodynamic platform arranged to support wind-powered electricalgenerators suitable for harvesting wind energy and converting it toelectricity, the platform comprising: an airfoil; a support frameworkincluding a variable geometry tail boom that can be tilted with respectto the airfoil; a plurality of wind turbines suitable for generatingelectricity and suitable for being powered to generate lift sufficientto enable the platform to take flight using the powered turbines, theturbines mounted to the aerodynamic platform.
 2. The platform of claim 1wherein the plurality of wind turbines are electrically powered togenerate lift.
 3. The platform of claim 1 wherein the support frameworkincludes at least one lift generating member.
 4. The platform of claim 1configured such that when the platform rests on the ground: the tailboom extends substantially parallel to the ground; and the airfoil isarranged such that a leading edge of the airfoil points upward and theairfoil chord is at or near normal to the ground.
 5. The platform ofclaim 4 configured such that when the platform rests on the ground theturbine blades are arranged at or near parallel to the ground.
 6. Theplatform of claim 1 wherein the plurality of wind turbines compriseshrouded wind turbines.
 7. The platform of claim 1 wherein the platformincludes control surfaces capable of maneuvering the platform.
 8. Theplatform of claim 1 wherein the variable geometry tail boom includes anempennage and wherein the empennage includes at least some of thecontrol surfaces.
 9. The platform of claim 1 wherein the platformcomprises a portion of a power generation and management system having;a tether system that anchors the platform to the ground while theplatform is airborne; and a power transmission system that thattransmits energy from the turbines to a power station.
 10. The powergeneration and management system of claim 9 wherein the power generationand management system includes a control system that monitors andadjusts the performance of at least one of the platform, the turbines,the tether system, and the power transmission system.
 11. The powergeneration and management system of claim 9 wherein the power stationincludes energy storage elements and a power distribution network. 12.The power generation and management system of claim 11 wherein theenergy storage elements include at least one of a capacitive element, abattery element, and a superconducting magnetic energy storage system:and the power distribution network includes a power grid.
 13. The powergeneration and management system of claim 9 wherein the power generationand management system includes a control system that controls theperformance of at least one of the platform, the turbines, the tethersystem, and the power transmission system.
 14. The power generation andmanagement system of claim 13 further including a remote sensing systemcapable of measuring weather and wind conditions and wherein the controlsystem receives such information as inputs and accordingly adjusts theperformance of at least one of the platform, the turbines, the tethersystem, and the power transmission system.
 15. A method of enabling anaerodynamic platform that supports wind-powered electrical generators totake off from a surface, the method comprising: providing a tetheredaerodynamic platform that mounts a plurality of wind turbines andincludes an airfoil arranged with a variable geometry tail boom, theplatform being positioned on a surface such that such that the airfoilis oriented with its leading edge pointing upward and the blades of theturbines oriented to provide upward lift and such that the variablegeometry tail boom extends generally parallel to the surface; providingpower to the turbines sufficient to cause the turbine blades to rotateand generate lift causing the platform to rise from the surface;changing the angle between the surface and the tail boom as the platformrises and a portion of the tail boom remains in contact with thesurface; securing the boom in position once the variable geometry tailboom clears the ground, with the boom secured generally parallel with achord of the airfoil; using the powered turbines to enable the platformto climb to a desired altitude; and maneuvering the platform such thatthe secured tail boom pitches upward to enable the platform to attain adesired flight attitude.
 16. The method of claim 15 further includingflying the platform to a desired position.
 17. The method of claim 16further including: terminating the power supply to the turbines;rotating the turbine blades under wind power to generate electricity;and transmitting the generated electricity to the power station usingthe power transmission system.
 18. The method of claim 16 wherein flyingthe platform to a desired position comprises flying the platform to aposition relative to a wind that is optimized to produce the greatestamount of electricity.
 19. The method of claim 16 wherein flying theplatform to a desired position comprises flying the platform to at leastone of: a position that enables a desired length of tether to be used toanchor the platform in the position; a position that enables the tetherto attain a desired angle with the ground and the platform; a positionthat places the platform at a desired altitude; and a position thatenables a desired tension to be exerted on the tether.
 20. The method ofclaim 16 wherein flying the platform to a desired position comprisesflying the platform to a position in the jet stream.